Circuit breaker



June 7, 1960 J. D. FINDLEY, JR., E rAL 2,939,931

CIRCUIT BREAKER Filed Dec. 20, 1956 2 Sheets-Sheet 1 Il"r |36 |00 O3 WITNESSES INVENTORS i Joseph D. Findley,Jr. 8 6p Roswlrl C. Van Sickle.

0%# @,uM/w.

AfroRNEY June 7, 1960 J. D. FINDLEY, JR., ETAL 2,939,931

CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed Dec. 20, 1956 Fig. 5.

mio

'P lOl --LQIH Insulation Insulation magnet and latching means;

United States Patent O CIRCUIT BREAKER Joseph I). Findley, Jr., ForestHills, and Roswell C. Van Sickle, Wilkinsburg, Pa., assignors toWestinghouse Electric Corporation, East Pittsburgh, Pa., a corporationof Pennsylvania Filed Dec. 20, 1956, Ser. No. 629,606

12 Claims. (Cl. 20o- 104) This invention relates to circuit breakers andmore particularly to high-speed electromagnet tripping devices forcircuit breakers.

When a tractive electromagnet is used to trip a highspeed circuitbreaker, the fastest possible build-up of useful pull in the magnet isdesired. The initial rate of build-up of current and also pull islimited by the inductance of the coil. The inductance of the coil isdetermined by the total llux linkages with the turns of the coil. Someof the flux linkages are caused by useful ilux crossing the working airgap of the magnet and threading the coil. The inductance `due to theuseful flux cannot be avoided if the magnet is to do useful work.

In most electromagnets there is a considerable portion of the total linxthreading the coil or part of the coil which does not cross the workingair gap. This socalled leakage flux does not contribute to the magneticpull, but does cause inductance and thus reduces the rate of build-up ofcurrent and, therefore, of the magnet pull. It has been found that thisleakage llux may be temporarily suppressed or delayed by placing aconductor of good conductivity, such, for instance, as copper in thepath of the leakage ilux. Eddy currents in the copper retard thebuild-up of the leakage ilux and effectively reduce the inductanceof thecoil during the tripping period.

=It is an object of the invention to provide a circuit breaker with animproved high-speed tripping electromagnet embodying novel shieldingmeans for reducing the leakage flux to thereby reduce the inductance ofthe magnet coil during the working period.

Another object of the invention is to provide a circuit breaker with animproved high-speed tripping electromagnet having a fixed magnet yokeand an energizing coil Iembodying members of high conductivity disposedadjacent a considerable portion of the magnet yoke to reduce theinductance of the -magnet and increase the rate of rise of useful ux inthe air gap.

Another object of the invention is to provide a circuit lbreaker with animproved high-speed tripping electromagnet comprising a iixed magnetyoke and an energizing coil having shielding means of high conductivitydisposed about the magnet yoke to reduce the leakage tlux to" therebydecrease `the tripping time of the magnet.

`Other objects and advantages of the invention will be pointed out inthe following description and illustrated in the accompanying drawings,which disclose, by way of example,.the principle of the invention andthe best mode,

In said drawings: Fig. .1,is a vertical sectional view showing a circuitbreaker operating mechanism embodying the principles "Fig l;

Fig. 3 is an elevational view of the tripping electrolwhich has beencontemplated, of applying that principle.

2,939,931 Patented June 7, 1960 ICC Fig. 4 is a front elevational viewof the tripping mechanism;

Fig. 5 is a sectional view through the tripping electro- J magnet takenon line V-V of Fig. 3; and

Fig. 6 is an exploded view of the tripping electromagnet.

The circuit breaker is of the type disclosed in the patent to Joseph D.Findley, Jr., Patent No. 2,866,031 entitled Circuit Breaker, andassigned to the assignee of the instant invention.

The circuit breaker comprises generally a plurality of sets of separablecontacts (not shown), an operating mechanism indicated generally at 23,a trip device indicated generally at 25 and a closing solenoid indicatedgenerally at 27.

The moving contact structure for each pole of the breaker is connectedby means of an operating rod 45 and nuts 49 to a cross bar 51 which iscommon to all polesof the breaker. The cross bar 51 is pivotallyconnected at its ends by pivot pins 53 (only one being shown) to anoperating bell crank lever 55 which is pivotally mounted on a shaft 57supported in the spaced side members 59 (only one being shown) of agenerally U- shaped frame 61. The frame 61 is rigidly supported in thebreaker frame structure (not shown) by means of a cross member 13 and aplate 62.

In addition to the operating bell crank lever 55, the operatingmechanism consists of a closing lever 63 pivotally mounted on a shaft 65supported in the side members 59 of the frame 61. The closing lever 63is operatively connected by means of a link 67, to the moving armature69 of the closing solenoid 27. The link 67 is connected by means of apin 70 to the armature 69. rIhe operating lever 55 and the closing lever63 are connected by means of an underset toggle comprising toggle links73 and.75 which are pivotally connected :together by a knee pivot pin77. The toggle link 73 is pivotally connected by a pin 79 to one arm ofthe operating bell crank lever 55 and the toggle link is pivotallyconnected to the closing lever 63 by a pin 81 which also connects thelink 67 to the closing lever. The closing lever 63 is held in the closedposition by a spring biased latch 83 which normally engages a roller 85on the pin 81.

The toggle 73, 75 is releasably held in a slightly underset position, inorder to hold the breaker closed, by a latch member 87 which is pivotedon the shaft 65. A link -89 connects the knee 77 of the toggle 73, 75 tothe latch member 87 being pivotally connected to the latter by a pin 91.The latch member 87 is normally releasably held in latching orvholdingpositions by a balanced trigger latch 99 which is actuated to unlatchingpositions byA operations of the trip device 25. A latch roller 93,rotatably mounted on the latch member 87 by a pin 95, normally engages'the inner end 97 of the trigger latch 99 which is mounted for horizontal`movement by pivot means 101 supported on a cross bar 103 which is, inturn, mounted on the cross member 13 by means of bolts 105, and by abracket 107 secured to the under side of the cross bar y103.

The electromagnetic trip device 25 is supported on a front plate 109secured to the cross bar 103 and toV a cross member 15 by means ofscrews 111. The trip device comprises a fixed E-shaped laminated magnetyoke 113 (Figs. 3, 4, 5 and 6) rigidly supported between a top plate 115and a bottom plate 117, both made "of a plates 1'1'5 and 117. Anenergizing coil 126 surrounds I the center lleg of -the xed magnet yoke)113. A movable armature 1'27 is rigidlyfsecured to the lower end of aU-shapedarmature lever 1,29 (Figs. 1 and 4)- the spaced sideKrnemberso'f which are lpivotally mounted 'on a Vpin 131 supported byandextending outwardly fromtheffront plate V109, the router VVend; ofrvthe 'pin' 4131 b'eingsupported in a bracket 13-3 4'which Ais `lrigidlysecured y'tothe "front plate 109. The lever 1A'1'29'is spaced from-theffrontplate 109 by a spacer 134. A member 135, secured Vtothe upper-endof the Alever 129, carriesfan adjusting screw 136, Awhich isadapted,upon Yenergization of the l electromagnet, to engag'e'the' outer lenel100-ofthe latch 99-to actuate the latch. The latch 99 Aisbiasedbyaspring 137 against anaadjustablefstop 1-39 y(Fig. 2') supported-on anupwardly extending Vportion 1410i the bracket 133 securedbyscrews L143to the frontplate 109. A spring '145 (Figs. 1 `and 4), v'coiled `about`the pin 131, biases the armature member 135 against a stop -147 .whichis also supportediby the portion 141 of 'the bracket 133.

When the electromagnet is energized in response to an overload current,it attracts the armature 127 and actuates the trigger latch 99 eectingrelease of the latch member 87. Upon release of the'latch member 87, thetoggle "73, 75 limmediatelycollapses toward the left causingclockwise'rotation ofthe operating bell crank lever l55 andopening ofthe breaker. vThe collapse of the toggle 73 75 Acauses counterclockwiserotation-of the togglelink 75 `about the 4pin 81 during whichrotation aprojection 149 on the toggle link 75 Iengages and moves the latch 83toits unlatching position. As soon' as the latch 83is'disengagedifrom'the'roller 85, a spring'1-51, connected under tensionbetween the armature 69 vof the closing solenoid and the cross bar 103,moves the armature 69 toward the left to its unattracted position. Thismovement of the armature, through the link 67, rotates the closing'lever63 in a clockwise direction resetting the toggle l73, 75 and relatchingthe'latchmember 87 Vwith the trigger latch 99. vThe leftward movement ofthe armature 69'isfarrested-by engagement ofthe link 67 with a. xed stop153. The-mechanism is now in condition to be closed by energization ofthe closing solenoid 27.

:Energization of the closing solenoid 27 attracts the armature 69 towardthe right which movement, through the link 67, rotates the `closinglever 63 counterclockwise about its pivot 65. Since the'latch member 87is now held by the'latch 99, the link -89 holds the toggle 73, 75 in`thrust Itransmitting 'condition causing the toggle to transmit'theforce "of the armature 69 to the operating bell crank'lever 55 whichthrusts the operating rod y '45 upwardly to close the breaker.. At theend of the closing stroke the latch-83 reengages the rollers 85 andholds the mechanism in the closed position.

YAn'irnportant feature of the invention'is the construction andarrangement of the tripping electromagnet whereby the? leakage ux isreduced which reduces the inductance of the energizing coil andincreases Vtheinitial `rate of rise of ilux across the'working air gapand with it, the rate of build-up of the pull of the magnet. It has beenfound that by placing pieces of a material of high conductivity/,'such,forY instance, as copper in the pathofunusable leakage flux, the eddycurrents in the conductive material retard the build-up of the leakageuiilr vandfelectively reduce the initial inductance of thel co Referringto Figs. `3, Siand 6, the electromagnet comprises, zas :previously:.described, the fixed .iE-shapedv magnet yoke..1.13 .rigidly held.between the upper-,and lower .platesll andzlll :respectively by,thebolts 119. The '11131651115 V2and...117.;ate .madeoa material havinghigh .cpnduetivitmsucln.for instance,:as::copper. Between the'p1ates1115 1\and .117 respectively, .and z the magnet yoke i113 aredisposed ...U ,shaped-.pieces -ofv insulation 15.5. A.UsshapedstriplSTpf insulation surrounds .three4 edges ing material isdisposed around the insulating strip 157 and `between the latter andthebolts 11-9 as clearly-seen in Figs. 3 and 5. Strips l161 of conductingmaterial disposed one on each side of the coil 126 between the coil andthe outer legs of the magnet yoke, have their inner ends formed at rightangles toward each other between the inner end of the coil and 'themagnetr yoke. Insulat ing strips 163 of .the-sameshape as 4theconducting strips 161 are disposed between the latter and the outer legs'ofthemagnet yoke.

The 'facing sides of thelplates 115-and 117 are recessed as 4at v*165 toreceive the coilV 126 and the spool -1767 yon which it is wound. Spacers169 of lconducting-material are placed in .the grooves 165 betweentheinner end of the coil 1'26 and outer end of the plates 115 and 117, andare held in-placeby"one of the"bolts"1'19 which passes through openingsin the plates and 117 and in the spacers 169. j

'The plates 1'15and "117 (Figs. k5 and 6) extend-downwardly adjacent"the sides of the armature 127 and the endsA of the U-shaped conductingstrip-1,59 extend down.- wardly adjacent the ends of the armature 127.This arrangement prevents vthe ilux from Haring outward to the'sides-ofthe'endpole faces and concentrates* the flux directlyj across the airgaps thereby increasing `the pull on the armature.

It -will be seen that all of the surfaces ofthe magnet yoke, except thecenter'leg of themagnet yoke and-thc Vthree'polefaces, have a conductivepath adjacent them.

Tests'on one embodiment of the invention have *shown that the use ofsuch-'conductive paths reduced the coil inductance from .024 henry to.'017 henry. "Ihis reduced the time to'reach 63% pull from .007 secondto .005second which reduced the tripping time .002 second or 29%. j

The yfast `interrupting time provided by the invention will'effectconsiderable'reduction in wire damage in clearing faults on overheadlines, thereby permitting improved continuity of 'service and reducelinemaintenance. Y

Having described the invention in accordance with the provisions of thepatent statutes, it is to lne/understood that various changes andmodifications may be madein the structural details land in thearrangement vof `parts without departing from the spirit of theyinvention.

We claim as our invention:

.1. An electromagnetic trip Vdevice'ior a circuit breaker comprising amagnet yoke, a pair ofspacedfrigid members of highly conductive materialdisposed on opposite sides of said magnet yoke, energizing means on saidmagnet` yoke, and a plurality of conducting'members of highly conductivematerial disposedadjacent the edge portions of said magnet'yoke tovreduce-'the leakage-'tink of said magnet yoke and thereby increase therate rof build-up of useful tlux.

2. An electromagnetic trip device for a circuit breaker comprising alaminated magnet yoke, *a* pair of spaced rigid members of 'a highly`conductive -material between which said laminated magnet yoke isdisposed, a U-shaped strip otra highly conducting material disposedadjacent three edges of said laminated 4magnet yoke to reduce theleakage ux of said magnet yoke.

3. An electromagnetic trip device'for -a circuit-breaker comprising amagnet yoke, a pair of'rigidV members of highly conductive-materialsupporting said 'magnetyokc between them, members of insulating materialdisposed Vbetween said rigid members and-said magnet yoke, 1a

`bers of a., highly conductivesmaterialhavingtsaid E-Shtlped magnet yokedisposed betweenthem,angcnellillgcoil/ mounted on the center leg of saidmagnet yoke, and conducting strips of a highly conductive materialadjacent the edge portions of said magnet yoke, said rigid members andsaid conductive strips reducing the leakage flux of said magnet yoke.

5. An electromagnetic trip device for a circuit breaker comprising alaminated E-shaped magnet yoke, a pair of relatively thick plates of ahighly conductive material disposed one on each side of said magnetyoke, an energizing coil mounted on one of the legs of said E-shapedmagnet yoke, and conducting strips of a highly conductive materialdisposed adjacent portions of the edges of said laminated magnet yoke,said plates and said conducting strips reducing the leakage llux of saidmagnet yoke.

6. An electroresponsive device comprising a rectangular E-shaped magnetyoke, a pair of plates of a highly conductive material disposed onopposite sides of said magnet yoke, said plates being larger than saidmagnet yoke, securing means securing said plates together to supportsaid magnet yoke, an energizing coil mounted on the center leg of saidmagnet yoke, said plates being recessed to receive said energizingcoil,-and a U-shaped conducting strip of a highly conductive materialdisposed around three sides of said magnet yoke between said magnet yokeand said securing means, said plates and said conducting strip reducingthe leakage ilux of said magnet yoke.

7. An electroresponsive device comprising an' E-shaped laminated magnetyoke having three pole faces, a pair of plates of a highly conductivematerial disposed on opposite faces of said laminated magnet yoke andsecured together to mount said magnet yoke, yan energizing coilsurrounding the middle leg of said magnet yoke, a U-shaped conductingstrip of a highly conductive material surrounding the edges of saidmagnet yoke except the pole faces, conducting strips of a highlyconductive material disposed `between said coil and the inner edges ofthe outer legs of said magnet yoke, said plates and said conductingstrips reducing the leakage ux of said magnet yoke.

8. An electroresponsive device comprising an E-shaped laminated magnetyoke having three pole faces, a pair of plates of a highly conductivematerial disposed on opposite faces of said laminated magnet yoke andsecured together to mount said magnet yoke, members of insulatingmaterial between said plates and said magnet yoke, an energizing coilsurrounding the middle leg of said magnet yoke, a U-shaped conductingstrip of a highly conductive material surrounding the edges of saidmagnet yoke except the pole faces, conducting strips of a highlyconductive material disposed between said coil and the inner edges ofthe outer legs of said magnet yoke, insulating means between each ofsaid conducting strips and said magnet yoke, said plates and saidconducting strips reducing the leakage llux of said magnet yoke.

9. A tractive electroresponsive device comprising a magnet yoke, a pairo-f members of a highly conductive non-magnetic material disposed onopposite sides of said magnet yoke, and means of a highly conductivenonmagnetic material disposed adjacent the edge portions of said magnetyoke, insulating means disposed between said highly conductivenon-magnetic materials and said magnetic yoke, said insulating meansbeing substantially thin to enable said highly conductive non-magneticmaterials to be positioned in close enough proximity to said magnet yoketo effectively reduce the leakage flux and thereby increase the rate ofbuild-up of useful ux.

l0. A tractive electroresponsive device comprising a fixed magnet yokeand a movable armature, an energizing coil on said magnet yoke, 4andshielding means of a highly conductive non-magnetic material surroundingsaid magnet yoke except the portion adjacent said armature, saidshielding means being in close enough proximity to said magnet yoke toeffectively reduce the leakage flux in said magnet yoke to therebyincrease the rate of buildup of useful flux.

ll. A tractive electromagnetic device comprising a magnet yoke having aplurality of pole faces, a movable armature providing a plurality of airgaps, an energizing coil on said magnet yoke, a shield of a highlyconductive material surrounding said electromagnet except the portionthereof adjacent said armature, said shield being disposed proximate tosaid magnet yoke to reduce the leakage flux in said magnet yoke tothereby increase the rate of build-up of useful flux across said airgaps, and portions of said shield extending adjacent the ends of said`armature to elfect a concentration of flux at said pole faces.

l2. A tractive electromagnet comprising `a magnet yoke having aplurality of pole faces, a movable armature disposed adjacent said polefaces providing a plurality of air gaps, an energizing coil on said-magnet yoke, shielding means comprising a pair of members of a highlyconductive material disposed at opposite sides of said magnet yoke, ashield of a highly conductive material surrounding the edges of saidmagnet yoke proximate thereto except the pole faces, said shieldingmeans and said shield reducing the leakage ux to thereby increase thebuild-up of useful flux across said air gaps, and the end portions ofsaid shield extending beyond said pole faces and adjacent the ends ofsaid armature to effect concentration of flux at said pole faces.

References Cited in the file of this patent UNITED STATES PATENTS650,915 Scribner et al. June 5, 1900 1,576,155 Stevens Mar. 9, 19262,348,556 Matthias May 9, 1944

